Option-adjusted Spread (OAS)
Option-adjusted Spread (OAS)
Definition: (1) The spread over an issuer's spot rate curve, developed as a measure of the yield spread that can be used to convert dollar differences between theoretical value and market prices. (2) The cost of the implied call embedded in an MBS, defined as additional basis-yield spread. When added to the base yield spread of an MBS without an operative call produces the option-adjusted spread.
Definition: (1) The spread over an issuer's spot rate curve, developed as a measure of the yield spread that can be used to convert dollar differences between theoretical value and market prices. (2) The cost of the implied call embedded in an MBS, defined as additional basis-yield spread. When added to the base yield spread of an MBS without an operative call produces the option-adjusted spread.